#include <bits/stdc++.h>
using namespace std;
double sh(int a, int b, int c){
    double s = (a + b + c) / 2;
    return sqrt(s * (s - a) * (s - b) * (s - c));
}
int main(){
    int X1, Y1, X2, Y2, X3, Y3;
    cin >> X1 >> Y1 >> X2 >> Y2 >> X3 >> Y3;
    int a = X2 - X1;
    int b = Y3 - Y2;
    double c = sqrt(pow(a, 2) + pow(b, 2));
    cout << fixed << setprecision(2) << sh(a, b, c) << endl;
    return 0;
}